1. Field of the Invention
The present invention relates to a one-part organopolysiloxane gel composition, and more particularly to a one-part organopolysiloxane gel composition that displays favorable long term storage stability at room temperature.
2. Description of the Prior Art
In an addition reaction curing type organopolysiloxane composition (hereafter simply referred to as “the composition”) comprising an organohydrogenpolysiloxane containing hydrogen atoms bonded to silicon atoms (SiH groups), an organopolysiloxane containing alkenyl groups such as vinyl groups bonded to silicon atoms, and a platinum based catalyst, which is converted to a cured product through an addition reaction of the above SiH groups to the vinyl groups (a hydrosilylation reaction), it is already known that by adding any of a variety of addition reaction inhibitors together with the platinum based catalyst, the addition reaction curing process can be inhibited at room temperature, enabling an improvement in the long term storage stability, and that by then heating the composition at the time of use, the addition reaction can be accelerated, enabling curing to take place. Examples of known addition reaction inhibitors include acetylene based compounds (U.S. Pat. No. 3,445,420), sulfoxide compounds (U.S. Pat. No. 3,453,234), and hydroperoxide compounds (U.S. Pat. No. 4,061,609).
However, in compositions comprising an organohydrogenpolysiloxane with a monofunctional unit represented by the formula H(CH3)2SiO0.5, namely, an organohydrogenpolysiloxane with a SiH group at a molecular chain terminal, even if an addition reaction inhibitor such as those described above is added, the addition reaction curing of the composition cannot be effectively inhibited at room temperature, meaning the storage stability of the composition is unsatisfactory. Furthermore, in the case of compositions that combine an aforementioned organohydrogenpolysiloxane with a SiH group at a molecular chain terminal, with an alkenyl group containing organopolysiloxane with a branched structure, achieving long term storage stability at room temperature is even more difficult.
In order to resolve these problems, U.S. Pat. No. 4,584,361 discloses the use of amine compounds such as n-butylamine, N,N-dibutylaminopropylamine and N,N,N′,N′-tetramethylethylenediamine as inhibitors for the room temperature addition reaction of compositions comprising a branched organopolysiloxane containing vinyl groups and an organohydrogenpolysiloxane with a SiH group at a molecular chain terminal. However, because these amine compounds have low boiling points, the storage stability deteriorates in open systems, and furthermore, if the composition also contains inorganic fillers, then the amine compounds tend to adsorb to the surface of these inorganic fillers, causing a marked reduction in the addition reaction inhibiting effect, and these types of drawbacks have limited the effectiveness of such compositions.
Compositions containing a phosphite ester as the addition reaction inhibitor have also been disclosed in U.S. Pat. No. 3,188,300, Published Japanese translations of PCT international publication (kohyo) No. 2001-508096 (JP2001-508096A) (US counterpart: U.S. Pat. No. 6,300,455), and Published Japanese translations of PCT international publication (kohyo) No. 2001-527111 (JP2001-527111A) (US counterpart: U.S. Pat. No. 6,346,562), whereas Japanese Laid-open publication (kokai) No. Sho 56-20051 (US counterpart: U.S. Pat. No. 4,329,275) discloses the use of a phosphorus compound and an organic peroxide as the addition reaction inhibitor. However in the above publications, no mention is made of the use of a phosphite ester as an addition reaction inhibitor capable of effectively inhibiting the room temperature addition reaction in a composition comprising an organohydrogenpolysiloxane with a SiH group at a molecular chain terminal. In addition, in the case of compositions comprising a combination of an organohydrogenpolysiloxane with a SiH group at a molecular chain terminal, and an alkenyl group containing organopolysiloxane with a branched structure, absolutely no mention is made of the fact that the addition reaction at room temperature can be effectively inhibited using either a phosphite ester, or a combination of a phosphite ester and an organic peroxide.